This invention relates to a paper feeding apparatus which feeds a sheet of paper automatically to the platen of the printer.
This kind of the paper feeding apparatus is known by Japanese published unexamined patent application No. 57-1780, for example. It feeds a sheet of paper from the paper feed tray to a position on the platen of the printer by rotating forward the feed roller and the platen. Thereafter, the rotation of the feed roller is suspended so as to fix the sheet at one of its edges, and the platen is rotated backward so as to straighten a front edge of the sheet along the platen. Finally, both the feed roller and the platen are rotated forward again to feed the sheet to the printing position on the platen.
According to this conventional apparatus, a single paper feed motor rotates the platen and the feed roller forward as well as backward, and also suspends the rotation of the feed roller during the rotation of the platen. Therefore, a clutch mechanism is necessary between the motor and the feed roller, resulting in the complicated construction of the apparatus.
Another conventional paper feeding apparatus of this kind feeds forward a sheet of paper which is set between the platen and the paper guide roller, and then feeds it backward for a predetermined distance. As a result, a front edge of the sheet is brought into contact with a contact point of the platen and the paper guide roller so as to straighten the edge along the platen. When the feed direction of paper is reversed from forward to backward, a motor which has been rotated forward to rotate the platen is immediately rotated backward. Similarly, when the direction is reversed from backward to forward, the motor which has been rotated backward is immediately rotated forward.
According to the aforementioned second prior art, the inertia force of the sheet or the vibration of the platen, in response to the reverse action of the platen, may weaken the contacting pressure between the sheet and the platen. Accordingly, the sheet sometimes fails to follow the rotation of the platen and slips on the platen, resulting in inaccurate paper feed.